Method of repairing cracked iron chills

ABSTRACT

A process for repairing cracked iron chills used in steelmaking wherein a cover comprising several coils is wound round the iron chill to prevent extension of the crack.

United States Patent 91 Evertz et a1. Y

[ METHOD OF REPAIRING CRACKED IRON CIIILLS [75] Inventors: Egon Evertz; Rolf Seybold, both of Solingen, Germany [73] Assignee: Egon Evertz, Solingen, Germany 22 Filed: Aug. 17', 1973 [21] Appl. No.: 389,218

Related US. Application Data [63] Continuation of Ser. No. 188,627, Oct. 12, 1971,

abandoned.

[30] Foreign Application Priority Data 6 Oct. 24, 1972 Germany ..2052327 [52] 11.5. C1 .2 29/402, 29/401, 164/411 [51] Int. Cl B23p 7/00 [58] Field of Search 29/401, 402; 52/514;

[56] References Cited UNITED STATES PATENTS 2,259,232 10/1941 Stone.; 29/401 X 1 May 7,1974

1/1968 Buschmann 29/401 3,530,564 9/1970 Cullen 29/401 3,758,939 9/1973 Galvani 29/402 FOREIGN PATENTS OR APPLICATIONS 276,332 7/1970 U.S.S.R..'. ..'l64/411 1,369,342 7/1964 France 29/402 Primary Examiner-Charles W. Lanham Assistant Examiner-D. C. Reiley Attorney, Agent, or Firm-I-Io1man & Stern [5 7] ABSTRACT 9 Claims, No Drawings 1 METHOD OF REPAIRING CRACKEDYIRON CHILLS This is a continuation, of application Ser. No. 188627, filed Oct. 12, 1971 now abandoned.

The invention relates to a process for repairing iron chills used in steelmaking which have been damaged by longitudinal cracks.

In known processes for repairing such cracked chills steelplates are used to cover the cracks which usually extend from the top edge of the iron chill. The plates can be secured on both sides of the crack with bolts or rivets which are fixed into the wall of the iron chill. Measures such as these are needed to prevent the cracks from spreading further. However, since considerable forces act on the covering when the chili is in use this can also crack and in fact this can occur in particular if the cover-plates have large cross-sectional areas. On the other hand, cover-plates with small crosssections are not able to withstand the strains acting on them.

The object'of the invention is to provide an improved repair process of the type described above so that the covering cannot crack even though it does not have the large cross-sectional area usually required, the covering, however, being sufficiently strong to withstand the strains applied in use. This is achieved according to the invention by providing a cover which comprises a plurality of coils wound, around the iron chill.

The overall cross-sectional area of a cover according to the invention is considerably reduced as compared with known covers because the cover is held in position essentially by the frictional forces developed by the coils. Also, cross-sectional weaknesses in, the cover, which may otherwise be caused by the fitting of rivets or bolts which are under shearing stress, are largely removed. There is even a considerable advantage compared with a ring-shaped cover, in the form of a shrunkon-ring, because as a rule the smaller individual crosssections of the individual covering coils taken together, have a greater strength than the larger full cross-section of a ring with the same steel quality. Since the transverse contraction of thinner cross-sections extends over a considerably larger area than that of thicker cross-sections, the expansion is also considerably more, so that a cover according to the invention, contrary to other covers, cannot crack but at most goes into a plastic deformation if the stress limit is exceeded. The cross-sectional area of the individual coils of the cover can be selected so that if there is any strain only a uniform expansion occurs which works along the whole length. Compared with covers which are riveted or bolted on to the chill on both sides of a crack, a considerable saving in material is achieved, even if the riveted or bolted cover extends over more than half the area of the iron chill, because the overall length of the cover according to the invention does not then have to be increased in relation to thereduction in the crosssectional area which is achieved.

The cover described by the invention can be made by coils formed by winding a steel strip around the cracked iron chill. The coils may be twisted in at least one place or may alternately'be wound in a flat spiral or overlapping formation. The trailing. end of the steel band can be riveted to the iron chill while the leading end of the steel band can be weldedto the previous coil or to the wall of the iron chill outside the area of the other coils. During the winding process the steel band is conveniently heated in those parts which extend around the corners of the iron chill.

It is advantageous if the coils are made from steel strip which may have in particular a thickness of about 2 5 mm. Moreover it is also possible to make the coils from wire rope or iron drawn bar steel of, for example, square cross-section.

If a cover according to the invention has been permanently stretched while the iron chill has been in use, it is advantageous, particularly in embodiments in which neither the start of the coiled cover nor the end of it is joined with the wall of theiron chill, to provide securing bolts under the coils, said bolts projecting sideways from the wall of the iron chill so that the covering cannot fall down when the chill cools. Securing bolts such as these are also an advantage with covering coils which are joined at both ends to the wall of the iron chill because in this way the intermediate coils are prevented from slipping down.'The effects of a permanent deformation such as this can be easily compensated for by one or more wedges which are driven in between the wall of the iron chill and the adjoining coils. By driving in wedges of this kind the whole cover is again tightened until the desired holding effect is again established.

To illustrate the invention a comparison is made in the following with a covering which has been riveted to a chill in a known manner on both sides of a crack.

, A rectangular heavy plate blank, 360 mm wide and 20 mm thick was provided to cover a crack which extends from the top edge of the iron chill. Six rivets, each having a diameter of 30 mm, were used to rivet the cover at both ends. At each end, through the riveting, a plate cross-section of 36 cm remains which may be subjected to stress. Compared to this, the six rivets have a total cross-sectional areaof 42 cm which is also subjected to stress. The cross-sectional area of the rivets which is subject to stress is therefore larger than the cross-sectional area of the plate which is subject to stress. The total cross-sectional area of the heavy plate (intermediate the ends) is 72 cm in this arrangement.

if, compared with this, only three coils are provided for a cover according to the present invention then only half the above-mentioned cross-sectional area will be sufficient. As was mentioned previously this is because frictional forces between the wall of the iron chill and the coils or between said coils can be made use of. Thus, with a coil, the ratio of the tensions in the two ends of a coil equals e', where t represents the coefficient of friction and a the radian measure of the arc of contact of the coil. With a coefficient of friction 0.2 and a value of a corresponding to three windings, the exponential expression above takes the numerical value 43, so that then only a small part (namely l/43rd) of the cross-sectional area which is subject to shearing stress is required for actually securing the coils. Therefore the cover cross-section remains practically unweakened and the coils can be made of strips of plate which have a total cross-sectional area of approximately only 36 cm in radial section.

The riveting of the first coil to the wall of the iron chill is preferably carried out, if the coils are arranged so that they lie in spiral formation on top of each other, with the heads of the rivets lying flush with the outer surface of the first coil, while the end of the last coil can be secured in a suitable mannerto a shacklewhich makes it possible at the same time for the coils to be vertically supported, as already mentioned, if they should become permanently deformed.

We claim:

1. A process for repairing iron chills used in steelmaking and which have been damaged by longitudinal cracks, said process comprises securing a trailing end of a steel band, spirally winding the steel band around the cracked areas a plurality of times thereby forming a plurality of coils arranged one on top of another, said coils being held in position essentially by frictional forces, and securing a leading end of the steel band.

2. A process as claimed in claim 1, wherein the coils are twisted in at least one place.

3. A process as claimed in claim 1 wherein the trailing end-of the steel band is riveted to the iron chill.

4. A process 'as claimed in claim 1, wherein the leading end of the steel band is welded to the previously formed coil.

5. A process as claimed in claim 1, wherein the leading end of the steel band is riveted to the wall of the iron chill.

6. A process as claimed in claim 1 where those parts of the steel band which are bent around the iron chill are heated.

7. A process as claimed in claim 1, where the steel band is about 2 mm to 5 mm thick.

8. A proces as claimed in claim 1 wherein securing bolts are provided which project from the wall of the iron chill.

9. A process as claimed in claim 1 where in wedges are driven in between the coils. 

1. A process for repairing iron chills used in steel-making and which have been damaged by longitudinal cracks, said process comprises securing a trailing end of a steel band, spirally winding the steel band around the cracked areas a plurality of times thereby forming a plurality of coils arranged one on top of another, said coils being held in position essentially by frictional forces, and securing a leading end of the steel band.
 2. A process as claimed in claim 1, wherein the coils are twisted in at least one place.
 3. A process as claimed in claim 1 wherein the trailing end of the steel band is riveted to the iron chill.
 4. A process as claimed in claim 1, wherein the leading end of the steel band is welded to the previously formed coil.
 5. A process as claimed in claim 1, wherein the leading end of the steel band is riveted to the wall of the iron chill.
 6. A process as claimed in claim 1 where those parts of the steel band which are bent around the iron chill are heated.
 7. A process as claimed in claim 1, where the steel band is about 2 mm to 5 mm thick.
 8. A proces as claimed in claim 1 wherein securing bolts are provided which project from the wall of the iron chill.
 9. A process as claimed in claim 1 where in wedges are driven in between the coils. 